Rotary data coupler

ABSTRACT

Various examples are directed to a rotary coupler and methods of use thereof. The rotary data coupler may comprise a transmitter and receiver. The transmitter may comprise a first band and a second transmitter band. The receiver may comprise a receiver housing positioned to rotate relative to the first transmitter band and the second transmitter band. A first receiver band may be positioned opposite the first transmitter band to form a first capacitor and a second receiver band may be positioned opposite the second transmitter band to form a second capacitor. The receiver may also comprise a resistance electrically coupled between the first receiver band and the second receiver band and a differential amplifier. The differential amplifier may comprise an inverting input and a non-inverting input, with the non-inverting input electrically coupled to the first receiver band and the inverting input electrically coupled to the second receiver band.

FIELD OF THE DISCLOSURE PRIORITY CLAIM

The present application is a continuation of U.S. application Ser. No.16/669,180 having a filing date of Oct. 30, 2019, which is acontinuation of U.S. application Ser. No. 16/186,056 having a filingdate of Nov. 9, 2018, which is a continuation of U.S. application Ser.No. 15/816,700 having a filing date of No. 17, 2017. Applicant claimspriority to and the benefit of each of such applications andincorporates all such applications herein by reference in its entirety.

BACKGROUND

In many applications, it is desirable to transmit an electrical signalacross a rotating interface. Various types of rotary data couplers canbe used. A slip-ring rotary data coupler includes a ring that is inphysical contact with a brush. As the ring rotates relative to thebrush, current is conducted at the physical interface between thecomponents. In an inductive rotary data coupler, a transmitter componentgenerates a magnetic field from an electrical signal. The magnetic fieldinduces a current indicative of the transmitted electrical signal in areceiver component.

DRAWINGS

In the drawings, which are not necessarily drawn to scale, like numeralsmay describe similar components in different views. Like numerals havingdifferent letter suffixes may represent different instances of similarcomponents. Some embodiments are illustrated by way of example, and notof limitation, in the figures of the accompanying drawings.

FIG. 1 is diagram showing one example of a rotary data coupler andcomponents for use therewith.

FIG. 2 is a diagram showing another example of a rotary data coupler andcomponents for use therewith.

FIG. 3 is a diagram showing one example environment for utilizing arotary data coupler.

FIG. 4 is a flowchart showing one example of a process flow that may beexecuted, for example, utilizing a rotary data coupler, such as therotary data couplers shown in FIGS. 1-3.

FIG. 5 is a block diagram illustrating a computing device hardwarearchitecture, within which a set or sequence of instructions can beexecuted to cause a machine to perform examples of any one of themethodologies discussed herein.

DESCRIPTION

Various examples are directed to rotary data couplers that may be used,for example, to transmit an electrical signal across a rotatinginterface. A rotating interface includes components that partially orfully rotate relative to one another. Rotating interfaces occur in manydifferent types of electrical and/or electromechanical devicesincluding, for example, systems with rotatable sensors or sensor arrays,such as Radio Detection and Ranging (RADAR), Light Detection and Ranging(LIDAR), vehicles with wheels, such as cars, trucks, trains, etc.

Rotary data couplers are used in various applications where it isdesirable to transmit an electrical signal across a rotating interface.For example, a rotating LIDAR system generates an electrical signalindicating sensed data. A rotary data coupler, such as the rotary datacouplers described herein, may be used to transmit the electrical signalfrom the rotating LIDAR system to another component that does not rotatewith the LIDAR system, such as a control circuit for the LIDAR, anothersystem component, etc. In another example, a sensor or other electricalcomponent may be positioned on a wheel, hub, or other rotating piece avehicle. The sensor may generate data that is to be transmitted to acontrol circuit or other system of the vehicle while the wheel or hub isrotating. A rotary data coupler, such as the rotary data couplersdescribed herein, may be used to transmit the data from the sensor tothe control circuit or other system.

An example rotary data coupler utilizes capacitive coupling to transmitan electrical signal (a transmitted signal) across a rotating interfacefrom a transmitter to a receiver. For example, the electrical signal isprovided at one or more transmitter bands. As charge accumulates at theone or more transmitter bands, an electric field is generated. Theelectric field brings about a corresponding charge at one or morereceiver bands. In some examples, the transmitter comprises first andsecond transmitter bands and the receiver comprises first and secondreceiver bands. The transmitter and receiver are arranged to align therespective transmitter and receiver bands. For example, the firsttransmitter band may be aligned with the first receiver band to form afirst capacitor. The second transmitter band is aligned with the secondreceiver band to form a second capacitor. When aligned, the respectivetransmitter and receiver bands are rotatable relative to one another.The first and second capacitors couple a signal and a reference valuefor the transmitted signal, which is received at the receiver as areceived signal.

Alignment of the various transmitter and receiver bands is accomplishedin any suitable manner. For example, the first and second transmitterbands may be wrapped at least partially around a circumference of atransmitter cylinder that is configured to fit within a receiver cavityof a receiver housing. The first and second receiver bands arepositioned around a cavity wall of the receiver housing. The transmittercylinder is received at least partially within the receiver cavity toalign the respective transmitter and receiver bands. The transmittercylinder is rotatable within the receiver cavity about an axis ofrotation. When the transmit signal is provided across the transmitterbands. The first and second capacitors conduct the transmit signalacross the rotating interface, with the received signal appearing acrossthe receiver bands.

Capacitive rotary data couplers, as described herein, may providevarious advantages over other types of rotary data couplers. Forexample, because the electrical signal is passed via an electric field,the transmitter and receiver may be arranged such that the transmitterand receiver bands do not come into physical contact with one another.This reduces mechanical wear on the coupler. Also, some capacitiverotary data couplers are capable of handling alternating current (A/C)signals at higher frequencies than can be handled by inductive couplersof comparable size.

The rotary data couplers described herein may be configured with asuitable frequency response. The frequency response of a rotary datacoupler describes the frequency content of the electrical signal that ispassed and/or attenuated. For example, the rotary data coupler isdescribed by a passband indicating a band or range of frequencies thatare transmitted across the first and second capacitors. The passband ofthe rotary data coupler is described by cutoff frequencies. A low cutofffrequency describes the low frequency range of the passband and a highcutoff frequency describes the high frequency range of the passband. Insome examples, the low and high cutoff frequencies are considered to bethe frequencies at which the transmitted signal is attenuated by 3 dB orto about half-power. Frequency content lower than the low cutofffrequency is attenuated at more than about 3 dB while frequency contenthigher than the low cutoff frequency is attenuated at less than about 3dB. The low cutoff frequency of the rotary data coupler may be describedby Equation [1] below:

$\begin{matrix}{f_{co} = \frac{1}{2\pi RC}} & \lbrack 1\rbrack\end{matrix}$In Equation [1], f_(co) is the low cut-off frequency of the rotary datacoupler. R is the resistance of the rotary data coupler, and C is thecapacitance of the rotary data coupler (e.g., based on the capacitanceof the first and second capacitors).

The rotary data coupler is configured with a passband that is positionedavoid attenuating data represented in the transmitted signal. Thetransmitted signal is a digital signal that represents data as a seriesof one or more discrete bits. The value of a bit may be represented by alevel of current and/or voltage in the transmitted signal. For example,a first level of voltage and/or current may represent logical one whilea second level of voltage and/or current may represent logical zero. Adata rate of the transmitted signal indicates the number of bitsrepresented by the transmitted signal per unit time. The analogfrequency content of the transmitted signal is based on the number oftransitions between logical one and logical zero per unit time. Therotary data coupler may be configured such transitions in the transmitsignal are within the passband of the rotary data coupler.

In some examples, the transmitted signal is encoded according to anencoding scheme that maintains a minimum number of transitions per unittime. Such an encoding scheme is used to keep the analog frequency ofthe transmitted signal above a minimum threshold. For example, if thetransmitted signal has an extended sequence where it does not transitionbetween logical one and logical zero, the analog frequency drops. If theanalog frequency drops below the low cut-off frequency of the rotarydata coupler, the transmitted signal is attenuated, causing distortion.On example encoding scheme that maintains a minimum number oftransitions per unit time is 8b/10b encoding. 8b/10b encoding representseach eight bit word of the transmitted signal as a corresponding ten bitsymbol, but also guarantees a transition between logical one and logicalzero at least once every five bits. Accordingly, the minimum number oftransitions per unit time is the data rate divided by five. Accordingly,when 8b/10b encoding is used, the lowest frequency content of datarepresented by the transmitted signal (e.g., indicated in Hz) is aboutone tenth of the data rate (e.g., indicated in bits per second).

Configuring the rotary data coupler with a passband that avoidsattenuating data in the transmitted signal may include setting a lowcut-off frequency of the rotary data coupler high enough to avoidsignificantly attenuating the lowest frequency content of the data. Insome examples, this includes setting the low cut-off frequency lowerthan about one half of the expected lowest frequency content of thetransmitted. Referring to Equation [1] above, this may be accomplishedby selecting the resistance and/or capacitance of the coupler to achievethe desired low cutoff frequency.

In practice, however, it may be challenging to select a high enoughcapacitance to achieve a desired low cutoff frequency. Capacitance of acapacitor is given by Equation [2] below:

$\begin{matrix}{C = \frac{\epsilon\; A}{d}} & \lbrack 2\rbrack\end{matrix}$In Equation [2], C is capacitance, ∈ is the absolute dielectric constantof the material between the capacitor elements (in this example, betweenrespective transmit and receive bands), A is the surface area of thecapacitor elements, and d is the distance between the capacitorelements. As shown, capacitance can be increased by increasing theabsolute dielectric constant, increasing the area of the bands, ordecreasing the distance between the bands. Increasing the absolutedielectric constant significantly may be difficult. Also, the area ofthe bands may be limited by the size of the rotary data coupler. Forexample, increasing capacitance by an order of magnitude or more wouldinvolve significantly increasing the size of the rotary data coupler.Further, significant decreases in the distance between receiver andtransmitter bands may lead to reduced mechanical tolerances, which mayrequire increased manufacturing expenses and lead to mechanical wear ifthe bands rub against each other.

In many implementations that utilize 8b/10b or similar encoding, such asPeripheral Component Interconnect Express (PCIe) or Serial Gigabit MediaIndependent Interface (SGMII), the transmitter and receiver areoptimized for 100 ohm differential transmission lines and terminations.For example, referring to Equation [1] above, a typical value for Rwould be about 100 ohms differentially or 50 ohms if analyzing one sideof the transmission individually. With this differential resistance,constructing a physical band structure that also meets the electricaland passband requirements can be challenging. For example, with theresistance at or near 100 ohms, the capacitance to meet the desiredcut-off frequency would lead to bands with very large areas or verysmall gaps between bands, which would lead to tight tolerances.

Instead of, or in addition to, increasing capacitance, various rotarydata couplers described herein introduce a receiver resistanceelectrically coupled between the first and second receiver bands.Referring to Equation [1] above, a receiver resistance may be selectedwith a high enough value to give the rotary data coupler a low cut-offfrequency that does not attenuate the expected lowest frequency of thetransmitted signal. Increasing the receiver resistance lowers thecurrent at the receiver. Accordingly, to aid in the detection of thereceiver signal, a differential amplifier may be electrically coupledbetween the first and second receiver bands. The differential amplifieramplifies a difference between current and/or voltage at the first andsecond receiver bands, providing the received signal at one or moreoutputs of the differential amplifier.

Rotary data couplers, as described herein, may have a passband thatencompasses transitions in the transmit signal (e.g., logical one tological zero or logical zero to logical one). In some examples, this mayallow the rotary data couplers described herein with common transceiverhardware and software (e.g., PCIe or SGMII transceivers) withoutresorting to more complex means of increasing transmit signal frequency,such as Manchester encoding or a similar encoding.

FIG. 1 is diagram showing one example of a rotary data coupler 100 andcomponents for use therewith. The rotary data coupler 100 includes atransmitter 101 and a receiver 103. The transmitter 101 includes atransmitter system 110 that generates a transmit signal 112. Thetransmit signal 112 may be a digital, differential signal manifestedbetween a positive transmit output T+ and a negative transmit output T−.The transmitter system 110 comprises any suitable system that generatesa transmit signal 112 to be coupled across a rotating interface. Oneexample transmitter system 110 is a rotating transceiver of a LIDARsystem that rotates to sense some or all of a panoramic field-of-view.

In the example of FIG. 1, the transmit signal 112 is provided at T+ andT−. A transmitter termination resistance 105 is provided between T+ andT−. The transmit signal is provided to transmitter bands 106A, 106B. Inthe example of FIG. 1, the transmitter bands 106A, 106B are at leastpartially wrapped around a transmitter cylinder 102. Although thetransmitter bands 106A, 106B are shown wrapped all the way around acircumference of the transmitter cylinder 102, in some examples, thetransmitter bands 106A, 106B do not extend around an entirecircumference of the transmitter cylinder 102.

The transmitter cylinder 102 is configured to fit within a receivercavity 118 of a receiver housing 104. Receiver bands 108A, 108B arepositioned on an interior wall of the receiver cavity 118, for example,at least partially around a circumference of an inside surface of thereceiver cavity 118. In some examples, the receiver bands 108A, 108B arepositioned at least partially around an outer circumference of thereceiver cavity 118. In examples in which the receiver bands 108A, 108Bare positioned at least partially around an outer circumference of thereceiver cavity 118, some or all of the material making up the receiverhousing 104 is between the respective receiver bands 108A, 108B andtransmitter bands 106A, 106B.

The transmitter bands 106A, 106B and the receiver bands 108A, 108B arepositioned such that the respective bands 106A, 108A and 106B, 108Balign when the transmitter cylinder 102 is received within the receiverhousing 104. Transmitter band 106A and receiver band 108A form a firstcapacitor while transmitter band 106B and receiver band 108B form asecond capacitor. The bands 106A, 108A, 106B, 108B may comprise anysuitable conductive material such as, for example, copper. In otherexamples, the transmitter and receiver may be reversed, such that areceiver cylinder may fit within a transmitter cavity.

The transmitter cylinder 102 and the receiver housing 104 are rotatablerelative to each other about an axis 127 of rotation. Rotation may be ineither direction or both directions indicated by arrow 125. In someexamples, the receiver housing 104 is stationary while the transmittercylinder 102 rotates about the axis 127. In alternative examples, thetransmitter cylinder 102 is stationary while the receiver housing 104rotates about the axis 127. In further examples, both the transmittercylinder 102 and the receiver housing 104 rotate about the axis 127. Agap 119 between the bands 106A, 108A, 106B, 108B may be at least about25 microns. The gap 119 may be between about 25 microns and about onemillimeter. In some examples, the gap 119 is at least about 1 millimetersuch as, for example, two or more millimeters. The gap 119 may bebetween the transmitter cylinder 102 and the receiver cavity 118 of thereceiver housing 104.

In addition to the receiver housing 104 and the receiver bands 108A,108B, the receiver 103 may include a receiver resistance 114, adifferential amplifier 116, and a receiver system 120. The receiverresistance 114 is electrically coupled between the first receiver band108A and the second receiver band 108B.

The transmitted signal 112 may be of a high enough frequency thattransmission line effects are relevant to the behavior of the circuit.For example, the transmitter system 110 has a characteristic impedance.The transmitter termination resistance 105 may be selected to match thecharacteristic impedance of the transmitter system 110, thus terminatinga differential transmission line between the transmitter system 110 andthe transmitter bands 106A, 106B. In various examples, othertransmission line termination techniques may be used in addition to orinstead of the transmitter termination resistance 105. In some examples,the transmitter system 110 has a characteristic impedance of about 50Ωsingle ended or a differential impedance of about 100Ω. In someexamples, the transmitter termination resistance 105 is selected tomatch a combined characteristic impedance of the transmitter system 110and one or more connections or other components between the transmittersystem 110 and the transmitter bands 106A, 106B.

The transmitted signal 112 may appear across the transmitter resistance105. Capacitors formed by the transmitter bands (e.g., a first capacitorincluding bands 106A, 108A and a second capacitor including bands 106B,108B) may also conduct the transmitted signal 112 where it also appearsacross the receiver resistance 114. The receiver resistance 114 isselected to generate a low cut-off frequency that is low enough to avoidexcessive attenuation of the low-frequency components of the transmittedsignal 112.

The size of the receiver resistance 114 is selected to achieve asuitable low cut-off frequency for the rotary data coupler 100. Inexamples where the capacitance of the first and second capacitors isabout 1 pf or less, the receiver resistance may be between about 1 kΩand about 100 kΩ. In some examples, the receiver resistance may bebetween about 50 kΩ and 44 kΩ. The receiver resistance 114 may behigher, in some examples two or more orders of magnitude higher, thanthe characteristic resistance of the combined transmitter system 110,bands 106A, 106B, 108A, 108B and other connections or components withoutcausing significant distortion due to signal reflection back towards thetransmitter system 110. For example, the terminating resistance 105 orother suitable transmission line termination mechanism, terminates thedifferential transmission line made up of the transmitter system 110 andother connections or components between the transmitter system 110 andthe transmitter bands 106A, 106B. This reduces or eliminates reflectionof the transmitted signal 112 back towards the transmitter system 110.The bands 106A, 106B, 108A, 108B, and receiver resistance 114, then, arepositioned in parallel to the differential transmission line. In thisway, a relatively high receiver resistance 114 may be selected withoutdeleterious transmission line effects causing excessive reflection ofthe transmitted signal 112.

When the receiver resistance 114 is high enough to bring about thedesired low cut-off frequency, it reduces the current in the receiver103. For example, if transmitted signal is between positive and negative1.2 volts, then the absolute value of the current at the receiverresistance 114 is a few hundred microamps or less. The differentialamplifier 116 is used to redrive the current and/or voltage across thereceiver bands 108A, 108B. The differential amplifier 116 has aninverting input (indicated by “−”) and a non-inverting input (indicatedby “+”). The non-inverting input is electrically coupled to the receiverband 108A and the inverting input is coupled to the receiver band 108B.In some examples, the differential amplifier 116 is selected with highinput impedance such that the current sourced and/or sunk by thedifferential amplifier 116 is small. A received signal 122 is providedat outputs of the differential amplifier 116, shown as R+ and R−.

When the transmitted signal 112 is a digital signal, the received signal122 is also a digital signal. The received signal 122 is provided to areceiver system 120. The receiver system 120 may be, or include, anysuitable system that receives a signal from the transmitter system 110.In examples where the transmitter system 110 is a LIDAR system, thereceived signal 122 indicates an output of the LIDAR system. Thereceiver system 120 may be, or include, a processing system forprocessing the output of the LIDAR system such as, for example,formatting the output, utilizing the output in a control system, etc.

FIG. 1 also shows a frequency response 130 for the rotary data coupler100. The horizontal axis 128 indicates frequency while the vertical axis126 indicates gain. A low cut-off frequency 132 is also shown. Thedesired maximum low cut-off frequency may be determined, for example,based on the nature of the transmitted signal 112. For example, if thetransmitted signal 112 is encoded by an encoding scheme that sets aminimum number of transitions per unit time, the lowest frequencycontent of the transmitted signal 112 is the minimum number oftransitions per unit time set by the encoding scheme (e.g., the minimumtransition frequency). For example, if the 8b/10b encoding scheme isused, the lowest frequency content of the signal is about equal to thedata rate divided by five. Accordingly when 8b/10b encoding is used, thelow cut-off frequency 132 may be selected to be about one tenth of thedata rate of the transmit signal. For example, if the transmit signal is2.5 Gb/s, the low cut-off frequency 132 may be about 250 MHz. In someexamples, the low cut-off frequency 132 is selected to be about onetenth of the data rate of the transmit signal, which is about one halfof one twentieth of the lowest frequency content.

Recalling that the low cut-off frequency is the frequency at which thetransmitted signal 112 is attenuated at 3 dB, or to half power, in someexamples, the low cut-off frequency is lower than the lowest frequencycontent of the transmitted signal 112 to incorporate a safety margin. Insome examples where the transmitted signal 112 is encoded utilizing8b/10b encoding, with a minimum transition frequency at one tenth thedata rate, the low cut-off frequency is set lower than one tenth thedata rate, such as, for example, between about one tenth and about onetwentieth of the data rate. The rotary data coupler 100 may also have ahigh cut-off frequency 133 indicating the highest frequency content thatis passed (e.g., not attenuated). Frequency content above the highcut-off frequency 133, such as high frequency noise, is attenuated. Therotary data coupler 100 may be configured with a high cut-off frequencythat is at least higher than the data rate. In some examples, the rotarydata coupler 100 is configured with a high cut-off frequency that isseveral multiples of the data rate so as to avoid attenuating higherorder harmonics. For example, the high cut-off frequency 133 may beabout 2 GHz for a signal conforming to the PCIe Generation 1 standards.

In the arrangement of FIG. 1, the low cut-off frequency 132 is given byEquation [1] above, with the capacitances of the first capacitor (bands108A, 106A) and second capacitor (bands 108B, 106B) forming thecapacitance indicated by “C” and the resistance of the receiverresistance 114 forming the resistance indicated by “R.” In variousexamples, the combined capacitance of the first and second capacitors issmall, for example, between about 0.03 pF and about 10 pF. In someexamples, the combined capacitance of the first and second capacitors isbetween about 0.03 pF and 0.3 pF. The value of the receiver resistance114 may be selected to generate a low cut-off frequency 132 as describedherein. In one example where the capacitance of the first and secondcapacitors is about 0.3 pF, the value of the resistance 114 may be about44 kΩ.

FIG. 2 is a diagram showing another example of a rotary data coupler 200including a transmitter 201 and a receiver 203. In the example of FIG.2, receiver bands 208A, 208B fit inside of transmitter bands 206A, 206B.For example, the receiver bands 208A, 208B may be wrapped around acircumference of a receiver cylinder that fits within a transmittercavity of a transmitter housing. The transmitter bands 206A, 206B andthe receiver bands 208A, 208B may rotate relative to one another aboutan axis 226 as indicated by arrow 228, for example, similar to what isdescribed with respect to FIG. 1. In other examples the orientation maybe reversed such that a transmitter cylinder fits within a receivercavity of a receiver housing.

In the example of FIG. 2, the transmit signal, indicated by T+ and T− isprovided to coupling resistors 202A, 202B and coupling capacitors 204A,204B. A transmitter termination resistance including resistors 205A,205B is also shown, with a reference voltage Vref1 provided therebetween. For example, each resistor 205A, 205B may be about half of thetotal transmitter termination resistance.

At the receiver 203, receiver resistance includes two resistors 214A,214B that are also provided with a reference voltage Vref2. Thereference voltage may be ground, or any suitable reference. The outputof a differential receiver 216 is provided to coupling resistors 218A,218B and coupling capacitors 220A, 220B. The received signal, indicatedby R+ and R−, may be across a termination resistor 222.

The differential receiver resistance is a sum of the resistances of theresistors 214A, 214B. For example, the sum of the resistances of theresistors 214A, 214B may be between about 1 kΩ and about 100 kΩ. In someexamples, the receiver resistance may be between about 500Ω and 44 kΩ.In the arrangement of FIG. 2, the frequency response of the rotatingdata coupler is based on the first capacitor (bands 208A, 208A), thesecond capacitor (bands 208B, 208B), and resistors 202A, 202B, 214A,214B. This decouples the frequency response of the rotary coupler 100from the differential impedance of common to 8b/10b signals, whichallows for capacitors to be constructed with lower area, increased gapsor separation distance, and less focus on dielectric materials.

FIG. 3 is a diagram showing one example environment 300 for utilizing arotary data coupler 301. The environment 300 includes a vehicle 350 witha rotating sensor housing 352. The vehicle 350, in some examples, isautonomous or semi-autonomous. The sensor housing 352 rotates relativeto the vehicle 350 about the rotary data coupler 301. For example, thesensor housing 352 rotates about an axis of rotation 327 in one or moreof the directions indicated by arrows 325. The sensor housing 352comprises a sensor system 357 comprising one or more sensors such as,for example, LIDAR system sensors, RADAR system sensors, one or morecameras, etc. (e.g., visible spectrum cameras, infrared cameras, etc.),and/or other sensors.

In some examples, the sensor system 357 includes one or more activesensors such as LIDAR sensors or RADAR sensors. A LIDAR sensor, forexample, includes one or more lasers or other sources of visible orinvisible light that are directed into the environment 300 around thevehicle 350. Reflections of the light are detected by one or morephotodiodes or other sensors. In a RADAR system, one or more antennastransmit electromagnetic waves (e.g., radio frequency radiation) intothe environment 300 around the vehicle 350. Reflections of theelectromagnetic waves are sensed by one or more receive antennas. Insome examples, a RADAR transmitter and receiver use a common antenna.

Outputs of the sensor system 357 are provided to a perception system 354(e.g., via the rotary data coupler 301). The perception system 354 isprogrammed to determine a location of the vehicle 350 and/or informationdescribing the environment 300 around the vehicle 350. For example,sensor data provided to the perception system 354 by one or more sensorsat the sensor housing, and/or other sensors, can include informationthat describes the location of objects within the surroundingenvironment 300 of the vehicle 350.

As one example, sensor data received from a LIDAR system includes thelocation (e.g., in three-dimensional space relative to the LIDAR system)of a number of points that correspond to objects that have reflected aranging laser. For example, a LIDAR system can measure distances bymeasuring the Time of Flight (TOF) that it takes a short laser pulse totravel from the sensor to an object and back, calculating the distancefrom the known speed of light. As another example, sensor data receivedfrom a RADAR system may include the location (e.g., in three-dimensionalspace relative to the RADAR system) of a number of points thatcorrespond to objects that have reflected a ranging electromagneticwave. Electromagnetic waves (e.g., pulsed or continuous) transmitted bythe RADAR system can reflect off an object and return to a receiver ofthe RADAR system, giving information about the object's location andspeed. Thus, a RADAR system can provide useful information about thecurrent speed of an object.

The perception system 354 receives sensor data from one or more sensors(including, for example, one or more sensors at the rotating sensorhousing 352) and derives information about the environment 300surrounding the vehicle 350 including, for example, a position of thevehicle 350 in the environment 300. Information derived by theperception system 354 is provided to a control system 356. The controlsystem 356 controls one or more functions of the car based on theinformation derived by the perception system 354 including, for example,throttle, braking, steering, etc. For clarity, the blocks representingthe perception system 354 and control system 356 are displayed outsideof the vehicle 350. These systems 354, 356 may be positioned within thevehicle 350, mounted to an exterior of the vehicle, remote from thevehicle 350, etc.

The example data coupler 301 shown in FIG. 3 is bidirectional. A firstchannel 303 is for transmitting data from the perception system 354 (orother system at the vehicle 350) to the sensor system 357. A secondchannel 305 is for transmitting data from the sensor system 357 to theperception system 354 (or other system at the vehicle 350). The firstchannel includes transmit bands 302, 304 that may be positioned torotate about the axis of rotation 327, for example, similar to transmitbands 106A, 106B, 208A, 208B described herein. A transmitter terminationresistance 310 may be present to terminate a transmission line betweenthe perception system 354 (or other system at the vehicle 350) and thetransmit bands 302, 304. Receive bands 306, 308 may form capacitors withthe respective transmit bands 302, 304, as described herein. A receivercircuit 312 includes a receiver resistance and differential amplifier,as described herein with respect to FIGS. 1 and 2.

In some examples, the channels 303, 305 utilize common housings. Forexample, transmitter bands 302, 304 and receiver bands 314, 316 may bepositioned on a first housing. For example, the bands 302, 304, 314, 316may be positioned on an interior wall of a cavity, such as the bands108A, 108B are positioned on an interior wall of the receiver cavity 118in FIG. 1. Similarly, transmitter bands 318, 320 and receiver bands 306,308 may be positioned on a second housing. For example, bands 306, 308,318, 320 may be wrapped around a cylinder, such as bands 106A, 106B arewrapped around the transmitter cylinder 102 in FIG. 1. The first andsecond housings may align corresponding transmitter and receiver bandsand may be rotatable relative to one another.

The second channel 305 may include transmit bands 318, 320 and receivebands 314, 316 similar to transmit bands 302, 304 and receive bands 306,308. The second channel 305 may also include a transmitter terminationresistance 322 and a receiver circuit 324 including a receiverresistance and differential amplifier, as described herein. In someexamples, bands 302, 304, 314, 316 are mounted on a first common housingwhile bands 306, 308, 318, 320 are mounted on a second common housing.

In some examples, the rotary data coupler 301 is unidirectional, forexample, with data being transmitted from the sensor system 357 to theperception system 354 only. Accordingly, the channel 303 may be omitted.Also, in other examples, bi-directional rotary data couplers, such as301, may be used in various other environments. Also, some rotary datacouplers may include multiple channels oriented in the same direction(e.g., to provide communications from the same transmitter system to thesame receiver system). For example, a single transmitter system mayutilize multiple channels to utilize multiple communication lands to thereceiver system.

The rotating data couplers described herein may be advantageous inrotating sensor housings for use with vehicles, such as the rotatingsensor housing 352 and the vehicle 350 of the environment 300. It may bedesirable for a rotating sensor housing 352 to be small enough to avoidprotruding beyond the roof of the vehicle 350. For example, the rotatingsensor housing 352 may be less than about 5 feet in diameter, less thanabout 4 feet in diameter, less than about 3 feet in diameter, etc. Also,in some examples, it may be desirable to minimize the mass of therotating sensor housing 352. The diameter of the rotating sensor housing352, in some examples is less than about 12 inches, less than about 6inches, less than about 4 inches, etc.

Also, in the environment 300 including a vehicle 350, which may be aself-driving vehicle, the rotating sensor housing 352 may house a LIDARand/or other sensor system that generates data at a high rate, such as,for example, between about 0.5 Gb/s and about 2.5 Gb/s. As describedhere, it may be desirable for the low cut-off frequency of the rotarydata coupler 301 to be between about one tenth of the data rate (e.g.,between about 50 MHz and about 250 MHz) and about one twentieth of thedata rate (e.g., between about 25 MHz and 125 MHz). In this environment300, the capacitive rotary data coupler 301, as described herein, may bewell suited to achieve the described frequency response while alsomeeting the described size constraints.

FIG. 4 is a flowchart showing one example of a process flow 400 that maybe executed, for example, utilizing a rotary data coupler, such as therotary data couplers 100, 200, 301 described herein. At operation 402, atransmitter system, such as transmitter system 110, generates a transmitsignal, such as the transmit signal 112. In some examples, the transmitsignal is a digital signal. In examples where the transmitter system isa LIDAR, RADAR, or other sensor array, the transmit signal representsoutputs generated by one or more sensors at the sensor array.

At operation 404, the transmitter of the rotary data coupler is rotatedrelative to the receiver of the rotary data coupler. This may includerotating the transmitter while keeping the receiver stationary, rotatingthe receiver while keeping the transmitter stationary, and/or rotatingboth the receiver and the transmitter. Rotation of the transmitterrelative to the receiver may be performed while the transmit signal isbeing generated at operation 402. For example, a sensor array maygenerate data while it is rotated.

At operation 406, the transmitter transmits the transmit signal acrossthe rotating rotary data coupler. For example, the transmitter providesa current and/or voltage representing the transmit signal across thetransmit bands (e.g., 106A, 106B) of the rotary data coupler. Atoperation 408, the receiver receives a received signal that, asdescribed herein, may appear across the receive bands (e.g., 108A, 108B)of the rotary data coupler. For example, the transmit signal causes acurrent through and/or voltage across the receiver resistance (e.g.,114) that indicates the transmit signal. The differential amplifierredrives that current and/or voltage, as described herein, to generatethe received signal at an output of the differential amplifier.

FIG. 5 is a block diagram illustrating a computing device hardwarearchitecture 500, within which a set or sequence of instructions can beexecuted to cause a machine to perform examples of any one of themethodologies discussed herein. The architecture 500 may describe, forexample, a transmitter system, such as the transmitter system 110 ofFIG. 1, a receiver system, such as the receiver system 120 of FIG. 1. Insome examples, the architecture 500 may also describe all or part of thesensor system 357, the perception system 354, the control system 356,etc.

The architecture 500 may operate as a standalone device or may beconnected (e.g., networked) to other machines. In a networkeddeployment, the architecture 500

may operate in the capacity of either a server or a client machine inserver-client network environments, or it may act as a peer machine inpeer-to-peer (or distributed) network environments. The architecture 500can be implemented in a personal computer (PC), a tablet PC, a hybridtablet, a set-top box (STB), a personal digital assistant (PDA), amobile telephone, a web appliance, a network router, a network switch, anetwork bridge, or any machine capable of executing instructions(sequential or otherwise) that specify operations to be taken by thatmachine.

The example architecture 500 includes a processor unit 502 comprising atleast one processor (e.g., a central processing unit (CPU), a graphicsprocessing unit (GPU), or both, processor cores, compute nodes, etc.).The architecture 500 may further comprise a main memory 504 and a staticmemory 506, which communicate with each other via a link 508 (e.g.,bus). The architecture 500 can further include a video display unit 510,an input device 512 (e.g., a keyboard), and a UI navigation device 514(e.g., a mouse). In some examples, the video display unit 510, inputdevice 512, and UI navigation device 514 are incorporated into atouchscreen display. The architecture 500 may additionally include astorage device 516 (e.g., a drive unit), a signal generation device 518(e.g., a speaker), a network interface device 520, and one or moresensors (not shown), such as a Global Positioning System (GPS) sensor,compass, accelerometer, or other sensor.

In some examples, the processor unit 502 or another suitable hardwarecomponent may support a hardware interrupt. In response to a hardwareinterrupt, the processor unit 502 may pause its processing and executean ISR, for example, as described herein.

The storage device 516 includes a machine-readable medium 522 on whichis stored one or more sets of data structures and instructions 524(e.g., software) embodying or utilized by any one or more of themethodologies or functions described herein. The instructions 524 canalso reside, completely or at least partially, within the main memory504, within the static memory 506, and/or within the processor unit 502during execution thereof by the architecture 500, with the main memory504, the static memory 506, and the processor unit 502 also constitutingmachine-readable media.

Executable Instructions and Machine-Storage Medium

The various memories (i.e., 504, 506, and/or memory of the processorunit(s) 502) and/or storage device 516 may store one or more sets ofinstructions and data structures (e.g., instructions) 524 embodying orutilized by any one or more of the methodologies or functions describedherein. These instructions, when executed by processor unit(s) 502 causevarious operations to implement the disclosed examples.

As used herein, the terms “machine-storage medium,” “device-storagemedium,” “computer-storage medium” (referred to collectively as“machine-storage medium 522”) mean the same thing and may be usedinterchangeably in this disclosure. The terms refer to a single ormultiple storage devices and/or media (e.g., a centralized ordistributed database, and/or associated caches and servers) that storeexecutable instructions and/or data, as well as cloud-based storagesystems or storage networks that include multiple storage apparatus ordevices. The terms shall accordingly be taken to include, but not belimited to, solid-state memories, and optical and magnetic media,including memory internal or external to processors. Specific examplesof machine-storage media, computer-storage media, and/or device-storagemedia 522 include non-volatile memory, including by way of examplesemiconductor memory devices, e.g., erasable programmable read-onlymemory (EPROM), electrically erasable programmable read-only memory(EEPROM), FPGA, and flash memory devices; magnetic disks such asinternal hard disks and removable disks; magneto-optical disks; andCD-ROM and DVD-ROM disks. The terms machine-storage media,computer-storage media, and device-storage media 522 specificallyexclude carrier waves, modulated data signals, and other such media, atleast some of which are covered under the term “signal medium” discussedbelow.

Signal Medium

The term “signal medium” or “transmission medium” shall be taken toinclude any form of modulated data signal, carrier wave, and so forth.The term “modulated data signal” means a signal that has one or more ofits characteristics set or changed in such a matter as to encodeinformation in the signal.

Computer Readable Medium

The terms “machine-readable medium,” “computer-readable medium” and“device-readable medium” mean the same thing and may be usedinterchangeably in this disclosure. The terms are defined to includeboth machine-storage media and signal media. Thus, the terms includeboth storage devices/media and carrier waves/modulated data signals.

The instructions 524 can further be transmitted or received over acommunications network 526 using a transmission medium via the networkinterface device 520 utilizing any one of a number of well-knowntransfer protocols (e.g., HTTP). Examples of communication networksinclude a LAN, a WAN, the Internet, mobile telephone networks, plain oldtelephone service (POTS) networks, and wireless data networks (e.g.,Wi-Fi, 3G, and 5G LTE/LTE-A or WiMAX networks). The term “transmissionmedium” shall be taken to include any intangible medium that is capableof storing, encoding, or carrying instructions for execution by themachine, and includes digital or analog communications signals or otherintangible media to facilitate communication of such software.

Throughout this specification, plural instances may implementcomponents, operations, or structures described as a single instance.Although individual operations of one or more methods are illustratedand described as separate operations, one or more of the individualoperations may be performed concurrently, and nothing requires that theoperations be performed in the order illustrated. Structures andfunctionality presented as separate components in example configurationsmay be implemented as a combined structure or component. Similarly,structures and functionality presented as a single component may beimplemented as separate components. These and other variations,modifications, additions, and improvements fall within the scope of thesubject matter herein.

Various components are described in the present disclosure as beingconfigured in a particular way. A component may be configured in anysuitable manner. For example, a component that is or that includes acomputing device may be configured with suitable software instructionsthat program the computing device. A component may also be configured byvirtue of its hardware arrangement or in any other suitable manner.

The above description is intended to be illustrative, and notrestrictive. For example, the above-described examples (or one or moreaspects thereof) can be used in combination with others. Other examplescan be used, such as by one of ordinary skill in the art upon reviewingthe above description. The Abstract is to allow the reader to quicklyascertain the nature of the technical disclosure, for example, to complywith 37 C.F.R. § 1.72(b) in the United States of America. It issubmitted with the understanding that it will not be used to interpretor limit the scope or meaning of the claims.

Also, in the above Detailed Description, various features can be groupedtogether to streamline the disclosure. However, the claims cannot setforth every feature disclosed herein, as examples can feature a subsetof said features. Further, examples can include fewer features thanthose disclosed in a particular example. Thus, the following claims arehereby incorporated into the Detailed Description, with each claimstanding on its own as a separate example. The scope of the examplesdisclosed herein is to be determined with reference to the appendedclaims, along with the full scope of equivalents to which such claimsare entitled.

The invention claimed is:
 1. A rotary data coupler comprising: arotatable cylinder comprising a cylindrical cavity; a transmitterlocated on and coupled to the rotatable cylinder; two or more firstbands positioned inside the cylindrical cavity of the rotatablecylinder; a cylinder positioned inside the cylindrical cavity; areceiver located on and coupled to the cylinder; and two or more secondbands attached to an outer surface of the cylinder, wherein each of thetwo or more first bands is aligned with a corresponding one of the twoor more second bands to form two or more pairs of aligned bands and toform a capacitive coupling across a gap between the aligned bands ofeach pair for transmitting a differential signal.
 2. The rotary datacoupler of claim 1, further comprising a line transmission terminator.3. The rotary data coupler of claim 1, further comprising a differentialreceiver resistance, wherein the differential receiver resistance isconfigured between the two or more second bands.
 4. The rotary datacoupler of claim 1, further comprising a differential amplifiercomprising an inverting input and a non-inverting input.
 5. The rotarydata couple of claim 4, wherein the non-inverting input is electricallycoupled to at least one of the capacitive couplings and the invertinginput being electrically coupled to at least one other of the capacitivecouplings.
 6. The rotary data coupler of claim 1, further comprising aLIDAR system comprising the transmitter and the receiver.
 7. The rotarydata coupler of claim 1, wherein one or more characteristics of thedifferential signal encode information.
 8. The rotary data coupler ofclaim 1, further comprising: two or more third bands attached to aninside surface of the cylindrical cavity of the rotatable cylinder; andtwo or more fourth bands attached to an outer surface of the cylinder,wherein each of the two or more third bands is aligned with acorresponding one of the two or more fourth bands to form two or moreadditional pairs of aligned bands and to form a further capacitivecoupling across a gap between the aligned bands of each pair of thirdand fourth bands.
 9. The rotary data coupler of claim 8, furthercomprising: a line transmission terminator between the two or more thirdbands, wherein at least one of the capacitive couplings and at least oneof the further capacitive couplings are configured for bi-directionaltransmissions.
 10. The rotary data coupler of claim 1, wherein the gapbetween each pair of the aligned bands is at least 1 millimeter.
 11. Therotary data coupler of claim 1, wherein a passband of the rotary datacoupler is configured with a low cut-off frequency and a high cut-offfrequency that avoids attenuating transitions in the differentialsignal.
 12. A light detection and ranging (LIDAR) system, comprising: arotating sensor housing configured to rotate about a rotary datacoupler, wherein the rotary data coupler comprises: a rotatable cylindercomprising a cylindrical cavity; a transmitter located on and coupled tothe rotatable cylinder; two or more first bands positioned inside thecylindrical cavity of the rotatable cylinder; a cylinder positionedinside the cylindrical cavity; a receiver located on and coupled to thecylinder; and two or more second bands attached to an outer surface ofthe cylinder, wherein each of the two or more first bands is alignedwith a corresponding one of the two or more second bands to form two ormore pairs of aligned bands and to form a capacitive coupling across agap between the aligned bands of each pair for transmitting adifferential signal.
 13. The LIDAR system of claim 12, wherein therotating sensor housing comprises a sensor system having one or moreLIDAR sensors.
 14. The LIDAR system of claim 12, wherein the sensorsystem is located on a vehicle.
 15. The LIDAR system of claim 14,further comprising a first channel for transmitting data from the LIDARsystem to another system of the vehicle and a second channel forreceiving data.
 16. The LIDAR system of claim 12, further comprising aline transmission terminator, wherein the line transmission terminatorreduces or eliminates reflection of the differential signal.
 17. TheLIDAR system of claim 12, further comprising a differential receiverresistance, wherein the differential receiver resistance is configuredbetween the two or more second bands.
 18. The LIDAR system of claim 12,wherein one or more characteristics of the differential signal arechanged to encode information.
 19. The LIDAR system of claim 12, whereina passband of the rotary data coupler is configured with a low cut-offfrequency and a high cut-off frequency that avoids attenuatingtransitions in the differential signal transmitted across the capacitivecouplings.
 20. A method of operating a rotary data coupler, the rotarydata coupler having a rotatable cylinder comprising a cylindricalcavity, a transmitter located on and coupled to the rotatable cylinder,two or more first bands positioned inside the cylindrical cavity of therotatable cylinder, a cylinder positioned inside the cylindrical cavity,a receiver located on and coupled to the cylinder, and two or moresecond bands attached to an outer surface of the cylinder, wherein eachof the two or more first bands is aligned with a corresponding one ofthe two or more second bands to form two or more pairs of aligned bandsand to form a capacitive coupling across a gap between the aligned bandsof each pair for transmitting a differential signal, the methodcomprising: rotating the transmitter relative to the receiver; providingthe differential signal at the two or more first bands while thetransmitter is rotating relative to the receiver; and receiving thedifferential signal at the two or more second bands while thetransmitter is rotating relative to the receiver.